**10. Acknowledgment**

306 Biogas

maximum of pollutions in the digestate. Pollutions mean toxic elements, physical contaminants and pathogen organisms. The quality of digestate products is regularly

Beside the fertilizer or amendment properties of digestate, nowadays there are some other ways to utilize it. These new methods are very creative and make the possibility of proper

A new promising alternative of the digestate utilization is its use as solid fuel after drying. Kratzeisen et al. (2010) used liquid digestate originated from silage maize co-digestion with different field crops and animal residues. After drying the digestate, the water content of pellets made was 9.2-9.9%. Their mechanical durability fulfilled the requirements of standards for pellets. Moreover, the calorific value of these pellets was similar to the calorific value of wood. Therefore digestate fuel pellet seems to be a good

Another interesting possibility of digestate utilization is the using of digestate effluent to replace freshwater and nutrients for bioethanol production. Gao & Li (2011) found that ethanol production was enhanced with digestate effluent by as much as 18% comparing to

Digestate can be separated to liquid and solid fraction. Liquid fraction is suitable for irrigation and it has high N and K content. Solid fraction contains a great amount of volatile solid and P (Liedl, et al., 2006) and – by its fertilizer effect – has also high biogas and methane potential, therefore it could be used as a co-ferment for anaerobic digestion (Balsari

The use of anaerobic digestion for treatment of solid and liquid organic wastes has vastly increased world-wide. The by-product of this process is the digestate, a liquid or solid material with high nutrient and organic matter content. These properties of the digestate make possible to use it as plant nutrients and to characterize it as a fertilizer. On the other hand, a biomass, reach in recalcitrant molecules is characterized by a high biological stability degree which is suitable for soil improving. The utilization of digestate as fertilizer provides economic and environmental benefits because of its higher stabile organic matter content, the hygienization effect of anaerobic digestion process and the reduced quantity of the artificial fertilizers needs for plant production. Moreover, the alkaline pH of digestate could contribute to the decrease of soil acidification, which is a serious problem of the world. Using digestate in place of artificial fertilizers could contribute to maintain the

As the results show, the digestate application in solid or liquid form could result significant improvement of the quantity and quality of foods through the even nutrient supply harmonizing with the necessity of plants and through its microelement content in the available forms for plants. In this way, digestate application in agriculture could contribute

controlled by "Bundesgütegemeinschaft Kompost e.V." (BGK) (Siebert et al., 2008).

**8. Future prospects** 

alternative fuel for wood.

the freshwater utilization.

et al., 2009)

**9. Conclusion** 

fertility of soil.

to the healthy life of humans.

utilization of digestates with different quality.

Our thanks to Dr. Judit Dobránszki at the University of Debrecen, Research Institute of Nyíregyháza and Prof. György Füleky at the Szent István University, Department of Soil Sciences and Agrochemistry for their enthusiastic checking of the English and for their valuable comments on improvements of the manuscript.
